Is this the same as what my bundler does?

No — this is whitespace and comment removal. A real minifier like terser or esbuild also renames local variables, drops dead branches and inlines constants, which cuts far more. Use your build tool for production; use this for a quick one-off.

Will it break my code?

It can, in one specific case: code that relies on automatic semicolon insertion. If your source omits semicolons and lines get joined, the meaning changes. Always test minified output, and prefer a proper minifier for anything you ship.

Is minified code obfuscated?

Not meaningfully. Minified JavaScript is smaller, not secret — any browser devtools can pretty-print it back. Never put a key or a secret in client-side code and expect minification to hide it.

JavaScript Minifier

Strip comments and unnecessary whitespace from JavaScript to reduce its size. Paste the source, copy the result. It runs in your browser, so proprietary code is never uploaded — which is the reason to prefer a local tool for this over an online one.

Runs in your browser — nothing is uploaded

Questions

Is this the same as what my bundler does?: No — this is whitespace and comment removal. A real minifier like terser or esbuild also renames local variables, drops dead branches and inlines constants, which cuts far more. Use your build tool for production; use this for a quick one-off.
Will it break my code?: It can, in one specific case: code that relies on automatic semicolon insertion. If your source omits semicolons and lines get joined, the meaning changes. Always test minified output, and prefer a proper minifier for anything you ship.
Is minified code obfuscated?: Not meaningfully. Minified JavaScript is smaller, not secret — any browser devtools can pretty-print it back. Never put a key or a secret in client-side code and expect minification to hide it.